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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.base;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import com.google.common.annotations.VisibleForTesting;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.io.Closeable;<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.io.FileNotFoundException;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.io.IOException;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.lang.ref.PhantomReference;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.lang.ref.Reference;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.lang.ref.ReferenceQueue;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.lang.reflect.Method;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.net.URL;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.net.URLClassLoader;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.util.logging.Level;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.util.logging.Logger;<a name="line.31"></a>
<span class="sourceLineNo">032</span><a name="line.32"></a>
<span class="sourceLineNo">033</span>/**<a name="line.33"></a>
<span class="sourceLineNo">034</span> * A reference queue with an associated background thread that dequeues references and invokes<a name="line.34"></a>
<span class="sourceLineNo">035</span> * {@link FinalizableReference#finalizeReferent()} on them.<a name="line.35"></a>
<span class="sourceLineNo">036</span> *<a name="line.36"></a>
<span class="sourceLineNo">037</span> * &lt;p&gt;Keep a strong reference to this object until all of the associated referents have been<a name="line.37"></a>
<span class="sourceLineNo">038</span> * finalized. If this object is garbage collected earlier, the backing thread will not invoke {@code<a name="line.38"></a>
<span class="sourceLineNo">039</span> * finalizeReferent()} on the remaining references.<a name="line.39"></a>
<span class="sourceLineNo">040</span> *<a name="line.40"></a>
<span class="sourceLineNo">041</span> * @author Bob Lee<a name="line.41"></a>
<span class="sourceLineNo">042</span> * @since 2.0 (imported from Google Collections Library)<a name="line.42"></a>
<span class="sourceLineNo">043</span> */<a name="line.43"></a>
<span class="sourceLineNo">044</span>public class FinalizableReferenceQueue implements Closeable {<a name="line.44"></a>
<span class="sourceLineNo">045</span>  /*<a name="line.45"></a>
<span class="sourceLineNo">046</span>   * The Finalizer thread keeps a phantom reference to this object. When the client (for example, a<a name="line.46"></a>
<span class="sourceLineNo">047</span>   * map built by MapMaker) no longer has a strong reference to this object, the garbage collector<a name="line.47"></a>
<span class="sourceLineNo">048</span>   * will reclaim it and enqueue the phantom reference. The enqueued reference will trigger the<a name="line.48"></a>
<span class="sourceLineNo">049</span>   * Finalizer to stop.<a name="line.49"></a>
<span class="sourceLineNo">050</span>   *<a name="line.50"></a>
<span class="sourceLineNo">051</span>   * If this library is loaded in the system class loader, FinalizableReferenceQueue can load<a name="line.51"></a>
<span class="sourceLineNo">052</span>   * Finalizer directly with no problems.<a name="line.52"></a>
<span class="sourceLineNo">053</span>   *<a name="line.53"></a>
<span class="sourceLineNo">054</span>   * If this library is loaded in an application class loader, it's important that Finalizer not<a name="line.54"></a>
<span class="sourceLineNo">055</span>   * have a strong reference back to the class loader. Otherwise, you could have a graph like this:<a name="line.55"></a>
<span class="sourceLineNo">056</span>   *<a name="line.56"></a>
<span class="sourceLineNo">057</span>   * Finalizer Thread runs instance of -&gt; Finalizer.class loaded by -&gt; Application class loader<a name="line.57"></a>
<span class="sourceLineNo">058</span>   * which loaded -&gt; ReferenceMap.class which has a static -&gt; FinalizableReferenceQueue instance<a name="line.58"></a>
<span class="sourceLineNo">059</span>   *<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * Even if no other references to classes from the application class loader remain, the Finalizer<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * thread keeps an indirect strong reference to the queue in ReferenceMap, which keeps the<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * Finalizer running, and as a result, the application class loader can never be reclaimed.<a name="line.62"></a>
<span class="sourceLineNo">063</span>   *<a name="line.63"></a>
<span class="sourceLineNo">064</span>   * This means that dynamically loaded web applications and OSGi bundles can't be unloaded.<a name="line.64"></a>
<span class="sourceLineNo">065</span>   *<a name="line.65"></a>
<span class="sourceLineNo">066</span>   * If the library is loaded in an application class loader, we try to break the cycle by loading<a name="line.66"></a>
<span class="sourceLineNo">067</span>   * Finalizer in its own independent class loader:<a name="line.67"></a>
<span class="sourceLineNo">068</span>   *<a name="line.68"></a>
<span class="sourceLineNo">069</span>   * System class loader -&gt; Application class loader -&gt; ReferenceMap -&gt; FinalizableReferenceQueue<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * -&gt; etc. -&gt; Decoupled class loader -&gt; Finalizer<a name="line.70"></a>
<span class="sourceLineNo">071</span>   *<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * Now, Finalizer no longer keeps an indirect strong reference to the static<a name="line.72"></a>
<span class="sourceLineNo">073</span>   * FinalizableReferenceQueue field in ReferenceMap. The application class loader can be reclaimed<a name="line.73"></a>
<span class="sourceLineNo">074</span>   * at which point the Finalizer thread will stop and its decoupled class loader can also be<a name="line.74"></a>
<span class="sourceLineNo">075</span>   * reclaimed.<a name="line.75"></a>
<span class="sourceLineNo">076</span>   *<a name="line.76"></a>
<span class="sourceLineNo">077</span>   * If any of this fails along the way, we fall back to loading Finalizer directly in the<a name="line.77"></a>
<span class="sourceLineNo">078</span>   * application class loader.<a name="line.78"></a>
<span class="sourceLineNo">079</span>   */<a name="line.79"></a>
<span class="sourceLineNo">080</span><a name="line.80"></a>
<span class="sourceLineNo">081</span>  private static final Logger logger = Logger.getLogger(FinalizableReferenceQueue.class.getName());<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span>  private static final String FINALIZER_CLASS_NAME = "com.google.common.base.internal.Finalizer";<a name="line.83"></a>
<span class="sourceLineNo">084</span><a name="line.84"></a>
<span class="sourceLineNo">085</span>  /** Reference to Finalizer.startFinalizer(). */<a name="line.85"></a>
<span class="sourceLineNo">086</span>  private static final Method startFinalizer;<a name="line.86"></a>
<span class="sourceLineNo">087</span>  static {<a name="line.87"></a>
<span class="sourceLineNo">088</span>    Class&lt;?&gt; finalizer = loadFinalizer(<a name="line.88"></a>
<span class="sourceLineNo">089</span>        new SystemLoader(), new DecoupledLoader(), new DirectLoader());<a name="line.89"></a>
<span class="sourceLineNo">090</span>    startFinalizer = getStartFinalizer(finalizer);<a name="line.90"></a>
<span class="sourceLineNo">091</span>  }<a name="line.91"></a>
<span class="sourceLineNo">092</span><a name="line.92"></a>
<span class="sourceLineNo">093</span>  /**<a name="line.93"></a>
<span class="sourceLineNo">094</span>   * The actual reference queue that our background thread will poll.<a name="line.94"></a>
<span class="sourceLineNo">095</span>   */<a name="line.95"></a>
<span class="sourceLineNo">096</span>  final ReferenceQueue&lt;Object&gt; queue;<a name="line.96"></a>
<span class="sourceLineNo">097</span><a name="line.97"></a>
<span class="sourceLineNo">098</span>  final PhantomReference&lt;Object&gt; frqRef;<a name="line.98"></a>
<span class="sourceLineNo">099</span><a name="line.99"></a>
<span class="sourceLineNo">100</span>  /**<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * Whether or not the background thread started successfully.<a name="line.101"></a>
<span class="sourceLineNo">102</span>   */<a name="line.102"></a>
<span class="sourceLineNo">103</span>  final boolean threadStarted;<a name="line.103"></a>
<span class="sourceLineNo">104</span><a name="line.104"></a>
<span class="sourceLineNo">105</span>  /**<a name="line.105"></a>
<span class="sourceLineNo">106</span>   * Constructs a new queue.<a name="line.106"></a>
<span class="sourceLineNo">107</span>   */<a name="line.107"></a>
<span class="sourceLineNo">108</span>  @SuppressWarnings("unchecked")<a name="line.108"></a>
<span class="sourceLineNo">109</span>  public FinalizableReferenceQueue() {<a name="line.109"></a>
<span class="sourceLineNo">110</span>    // We could start the finalizer lazily, but I'd rather it blow up early.<a name="line.110"></a>
<span class="sourceLineNo">111</span>    queue = new ReferenceQueue&lt;Object&gt;();<a name="line.111"></a>
<span class="sourceLineNo">112</span>    frqRef = new PhantomReference&lt;Object&gt;(this, queue);<a name="line.112"></a>
<span class="sourceLineNo">113</span>    boolean threadStarted = false;<a name="line.113"></a>
<span class="sourceLineNo">114</span>    try {<a name="line.114"></a>
<span class="sourceLineNo">115</span>      startFinalizer.invoke(null, FinalizableReference.class, queue, frqRef);<a name="line.115"></a>
<span class="sourceLineNo">116</span>      threadStarted = true;<a name="line.116"></a>
<span class="sourceLineNo">117</span>    } catch (IllegalAccessException impossible) {<a name="line.117"></a>
<span class="sourceLineNo">118</span>      throw new AssertionError(impossible); // startFinalizer() is public<a name="line.118"></a>
<span class="sourceLineNo">119</span>    } catch (Throwable t) {<a name="line.119"></a>
<span class="sourceLineNo">120</span>      logger.log(Level.INFO, "Failed to start reference finalizer thread."<a name="line.120"></a>
<span class="sourceLineNo">121</span>          + " Reference cleanup will only occur when new references are created.", t);<a name="line.121"></a>
<span class="sourceLineNo">122</span>    }<a name="line.122"></a>
<span class="sourceLineNo">123</span><a name="line.123"></a>
<span class="sourceLineNo">124</span>    this.threadStarted = threadStarted;<a name="line.124"></a>
<span class="sourceLineNo">125</span>  }<a name="line.125"></a>
<span class="sourceLineNo">126</span><a name="line.126"></a>
<span class="sourceLineNo">127</span>  @Override<a name="line.127"></a>
<span class="sourceLineNo">128</span>  public void close() {<a name="line.128"></a>
<span class="sourceLineNo">129</span>    frqRef.enqueue();<a name="line.129"></a>
<span class="sourceLineNo">130</span>    cleanUp();<a name="line.130"></a>
<span class="sourceLineNo">131</span>  }<a name="line.131"></a>
<span class="sourceLineNo">132</span><a name="line.132"></a>
<span class="sourceLineNo">133</span>  /**<a name="line.133"></a>
<span class="sourceLineNo">134</span>   * Repeatedly dequeues references from the queue and invokes {@link<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * FinalizableReference#finalizeReferent()} on them until the queue is empty. This method is a<a name="line.135"></a>
<span class="sourceLineNo">136</span>   * no-op if the background thread was created successfully.<a name="line.136"></a>
<span class="sourceLineNo">137</span>   */<a name="line.137"></a>
<span class="sourceLineNo">138</span>  void cleanUp() {<a name="line.138"></a>
<span class="sourceLineNo">139</span>    if (threadStarted) {<a name="line.139"></a>
<span class="sourceLineNo">140</span>      return;<a name="line.140"></a>
<span class="sourceLineNo">141</span>    }<a name="line.141"></a>
<span class="sourceLineNo">142</span><a name="line.142"></a>
<span class="sourceLineNo">143</span>    Reference&lt;?&gt; reference;<a name="line.143"></a>
<span class="sourceLineNo">144</span>    while ((reference = queue.poll()) != null) {<a name="line.144"></a>
<span class="sourceLineNo">145</span>      /*<a name="line.145"></a>
<span class="sourceLineNo">146</span>       * This is for the benefit of phantom references. Weak and soft references will have already<a name="line.146"></a>
<span class="sourceLineNo">147</span>       * been cleared by this point.<a name="line.147"></a>
<span class="sourceLineNo">148</span>       */<a name="line.148"></a>
<span class="sourceLineNo">149</span>      reference.clear();<a name="line.149"></a>
<span class="sourceLineNo">150</span>      try {<a name="line.150"></a>
<span class="sourceLineNo">151</span>        ((FinalizableReference) reference).finalizeReferent();<a name="line.151"></a>
<span class="sourceLineNo">152</span>      } catch (Throwable t) {<a name="line.152"></a>
<span class="sourceLineNo">153</span>        logger.log(Level.SEVERE, "Error cleaning up after reference.", t);<a name="line.153"></a>
<span class="sourceLineNo">154</span>      }<a name="line.154"></a>
<span class="sourceLineNo">155</span>    }<a name="line.155"></a>
<span class="sourceLineNo">156</span>  }<a name="line.156"></a>
<span class="sourceLineNo">157</span><a name="line.157"></a>
<span class="sourceLineNo">158</span>  /**<a name="line.158"></a>
<span class="sourceLineNo">159</span>   * Iterates through the given loaders until it finds one that can load Finalizer.<a name="line.159"></a>
<span class="sourceLineNo">160</span>   *<a name="line.160"></a>
<span class="sourceLineNo">161</span>   * @return Finalizer.class<a name="line.161"></a>
<span class="sourceLineNo">162</span>   */<a name="line.162"></a>
<span class="sourceLineNo">163</span>  private static Class&lt;?&gt; loadFinalizer(FinalizerLoader... loaders) {<a name="line.163"></a>
<span class="sourceLineNo">164</span>    for (FinalizerLoader loader : loaders) {<a name="line.164"></a>
<span class="sourceLineNo">165</span>      Class&lt;?&gt; finalizer = loader.loadFinalizer();<a name="line.165"></a>
<span class="sourceLineNo">166</span>      if (finalizer != null) {<a name="line.166"></a>
<span class="sourceLineNo">167</span>        return finalizer;<a name="line.167"></a>
<span class="sourceLineNo">168</span>      }<a name="line.168"></a>
<span class="sourceLineNo">169</span>    }<a name="line.169"></a>
<span class="sourceLineNo">170</span><a name="line.170"></a>
<span class="sourceLineNo">171</span>    throw new AssertionError();<a name="line.171"></a>
<span class="sourceLineNo">172</span>  }<a name="line.172"></a>
<span class="sourceLineNo">173</span><a name="line.173"></a>
<span class="sourceLineNo">174</span>  /**<a name="line.174"></a>
<span class="sourceLineNo">175</span>   * Loads Finalizer.class.<a name="line.175"></a>
<span class="sourceLineNo">176</span>   */<a name="line.176"></a>
<span class="sourceLineNo">177</span>  interface FinalizerLoader {<a name="line.177"></a>
<span class="sourceLineNo">178</span><a name="line.178"></a>
<span class="sourceLineNo">179</span>    /**<a name="line.179"></a>
<span class="sourceLineNo">180</span>     * Returns Finalizer.class or null if this loader shouldn't or can't load it.<a name="line.180"></a>
<span class="sourceLineNo">181</span>     *<a name="line.181"></a>
<span class="sourceLineNo">182</span>     * @throws SecurityException if we don't have the appropriate privileges<a name="line.182"></a>
<span class="sourceLineNo">183</span>     */<a name="line.183"></a>
<span class="sourceLineNo">184</span>    Class&lt;?&gt; loadFinalizer();<a name="line.184"></a>
<span class="sourceLineNo">185</span>  }<a name="line.185"></a>
<span class="sourceLineNo">186</span><a name="line.186"></a>
<span class="sourceLineNo">187</span>  /**<a name="line.187"></a>
<span class="sourceLineNo">188</span>   * Tries to load Finalizer from the system class loader. If Finalizer is in the system class path,<a name="line.188"></a>
<span class="sourceLineNo">189</span>   * we needn't create a separate loader.<a name="line.189"></a>
<span class="sourceLineNo">190</span>   */<a name="line.190"></a>
<span class="sourceLineNo">191</span>  static class SystemLoader implements FinalizerLoader {<a name="line.191"></a>
<span class="sourceLineNo">192</span>    // This is used by the ClassLoader-leak test in FinalizableReferenceQueueTest to disable<a name="line.192"></a>
<span class="sourceLineNo">193</span>    // finding Finalizer on the system class path even if it is there.<a name="line.193"></a>
<span class="sourceLineNo">194</span>    @VisibleForTesting<a name="line.194"></a>
<span class="sourceLineNo">195</span>    static boolean disabled;<a name="line.195"></a>
<span class="sourceLineNo">196</span><a name="line.196"></a>
<span class="sourceLineNo">197</span>    @Override<a name="line.197"></a>
<span class="sourceLineNo">198</span>    public Class&lt;?&gt; loadFinalizer() {<a name="line.198"></a>
<span class="sourceLineNo">199</span>      if (disabled) {<a name="line.199"></a>
<span class="sourceLineNo">200</span>        return null;<a name="line.200"></a>
<span class="sourceLineNo">201</span>      }<a name="line.201"></a>
<span class="sourceLineNo">202</span>      ClassLoader systemLoader;<a name="line.202"></a>
<span class="sourceLineNo">203</span>      try {<a name="line.203"></a>
<span class="sourceLineNo">204</span>        systemLoader = ClassLoader.getSystemClassLoader();<a name="line.204"></a>
<span class="sourceLineNo">205</span>      } catch (SecurityException e) {<a name="line.205"></a>
<span class="sourceLineNo">206</span>        logger.info("Not allowed to access system class loader.");<a name="line.206"></a>
<span class="sourceLineNo">207</span>        return null;<a name="line.207"></a>
<span class="sourceLineNo">208</span>      }<a name="line.208"></a>
<span class="sourceLineNo">209</span>      if (systemLoader != null) {<a name="line.209"></a>
<span class="sourceLineNo">210</span>        try {<a name="line.210"></a>
<span class="sourceLineNo">211</span>          return systemLoader.loadClass(FINALIZER_CLASS_NAME);<a name="line.211"></a>
<span class="sourceLineNo">212</span>        } catch (ClassNotFoundException e) {<a name="line.212"></a>
<span class="sourceLineNo">213</span>          // Ignore. Finalizer is simply in a child class loader.<a name="line.213"></a>
<span class="sourceLineNo">214</span>          return null;<a name="line.214"></a>
<span class="sourceLineNo">215</span>        }<a name="line.215"></a>
<span class="sourceLineNo">216</span>      } else {<a name="line.216"></a>
<span class="sourceLineNo">217</span>        return null;<a name="line.217"></a>
<span class="sourceLineNo">218</span>      }<a name="line.218"></a>
<span class="sourceLineNo">219</span>    }<a name="line.219"></a>
<span class="sourceLineNo">220</span>  }<a name="line.220"></a>
<span class="sourceLineNo">221</span><a name="line.221"></a>
<span class="sourceLineNo">222</span>  /**<a name="line.222"></a>
<span class="sourceLineNo">223</span>   * Try to load Finalizer in its own class loader. If Finalizer's thread had a direct reference to<a name="line.223"></a>
<span class="sourceLineNo">224</span>   * our class loader (which could be that of a dynamically loaded web application or OSGi bundle),<a name="line.224"></a>
<span class="sourceLineNo">225</span>   * it would prevent our class loader from getting garbage collected.<a name="line.225"></a>
<span class="sourceLineNo">226</span>   */<a name="line.226"></a>
<span class="sourceLineNo">227</span>  static class DecoupledLoader implements FinalizerLoader {<a name="line.227"></a>
<span class="sourceLineNo">228</span>    private static final String LOADING_ERROR = "Could not load Finalizer in its own class loader."<a name="line.228"></a>
<span class="sourceLineNo">229</span>        + "Loading Finalizer in the current class loader instead. As a result, you will not be able"<a name="line.229"></a>
<span class="sourceLineNo">230</span>        + "to garbage collect this class loader. To support reclaiming this class loader, either"<a name="line.230"></a>
<span class="sourceLineNo">231</span>        + "resolve the underlying issue, or move Google Collections to your system class path.";<a name="line.231"></a>
<span class="sourceLineNo">232</span><a name="line.232"></a>
<span class="sourceLineNo">233</span>    @Override<a name="line.233"></a>
<span class="sourceLineNo">234</span>    public Class&lt;?&gt; loadFinalizer() {<a name="line.234"></a>
<span class="sourceLineNo">235</span>      try {<a name="line.235"></a>
<span class="sourceLineNo">236</span>        /*<a name="line.236"></a>
<span class="sourceLineNo">237</span>         * We use URLClassLoader because it's the only concrete class loader implementation in the<a name="line.237"></a>
<span class="sourceLineNo">238</span>         * JDK. If we used our own ClassLoader subclass, Finalizer would indirectly reference this<a name="line.238"></a>
<span class="sourceLineNo">239</span>         * class loader:<a name="line.239"></a>
<span class="sourceLineNo">240</span>         *<a name="line.240"></a>
<span class="sourceLineNo">241</span>         * Finalizer.class -&gt; CustomClassLoader -&gt; CustomClassLoader.class -&gt; This class loader<a name="line.241"></a>
<span class="sourceLineNo">242</span>         *<a name="line.242"></a>
<span class="sourceLineNo">243</span>         * System class loader will (and must) be the parent.<a name="line.243"></a>
<span class="sourceLineNo">244</span>         */<a name="line.244"></a>
<span class="sourceLineNo">245</span>        ClassLoader finalizerLoader = newLoader(getBaseUrl());<a name="line.245"></a>
<span class="sourceLineNo">246</span>        return finalizerLoader.loadClass(FINALIZER_CLASS_NAME);<a name="line.246"></a>
<span class="sourceLineNo">247</span>      } catch (Exception e) {<a name="line.247"></a>
<span class="sourceLineNo">248</span>        logger.log(Level.WARNING, LOADING_ERROR, e);<a name="line.248"></a>
<span class="sourceLineNo">249</span>        return null;<a name="line.249"></a>
<span class="sourceLineNo">250</span>      }<a name="line.250"></a>
<span class="sourceLineNo">251</span>    }<a name="line.251"></a>
<span class="sourceLineNo">252</span><a name="line.252"></a>
<span class="sourceLineNo">253</span>    /**<a name="line.253"></a>
<span class="sourceLineNo">254</span>     * Gets URL for base of path containing Finalizer.class.<a name="line.254"></a>
<span class="sourceLineNo">255</span>     */<a name="line.255"></a>
<span class="sourceLineNo">256</span>    URL getBaseUrl() throws IOException {<a name="line.256"></a>
<span class="sourceLineNo">257</span>      // Find URL pointing to Finalizer.class file.<a name="line.257"></a>
<span class="sourceLineNo">258</span>      String finalizerPath = FINALIZER_CLASS_NAME.replace('.', '/') + ".class";<a name="line.258"></a>
<span class="sourceLineNo">259</span>      URL finalizerUrl = getClass().getClassLoader().getResource(finalizerPath);<a name="line.259"></a>
<span class="sourceLineNo">260</span>      if (finalizerUrl == null) {<a name="line.260"></a>
<span class="sourceLineNo">261</span>        throw new FileNotFoundException(finalizerPath);<a name="line.261"></a>
<span class="sourceLineNo">262</span>      }<a name="line.262"></a>
<span class="sourceLineNo">263</span><a name="line.263"></a>
<span class="sourceLineNo">264</span>      // Find URL pointing to base of class path.<a name="line.264"></a>
<span class="sourceLineNo">265</span>      String urlString = finalizerUrl.toString();<a name="line.265"></a>
<span class="sourceLineNo">266</span>      if (!urlString.endsWith(finalizerPath)) {<a name="line.266"></a>
<span class="sourceLineNo">267</span>        throw new IOException("Unsupported path style: " + urlString);<a name="line.267"></a>
<span class="sourceLineNo">268</span>      }<a name="line.268"></a>
<span class="sourceLineNo">269</span>      urlString = urlString.substring(0, urlString.length() - finalizerPath.length());<a name="line.269"></a>
<span class="sourceLineNo">270</span>      return new URL(finalizerUrl, urlString);<a name="line.270"></a>
<span class="sourceLineNo">271</span>    }<a name="line.271"></a>
<span class="sourceLineNo">272</span><a name="line.272"></a>
<span class="sourceLineNo">273</span>    /** Creates a class loader with the given base URL as its classpath. */<a name="line.273"></a>
<span class="sourceLineNo">274</span>    URLClassLoader newLoader(URL base) {<a name="line.274"></a>
<span class="sourceLineNo">275</span>      // We use the bootstrap class loader as the parent because Finalizer by design uses<a name="line.275"></a>
<span class="sourceLineNo">276</span>      // only standard Java classes. That also means that FinalizableReferenceQueueTest<a name="line.276"></a>
<span class="sourceLineNo">277</span>      // doesn't pick up the wrong version of the Finalizer class.<a name="line.277"></a>
<span class="sourceLineNo">278</span>      return new URLClassLoader(new URL[] {base}, null);<a name="line.278"></a>
<span class="sourceLineNo">279</span>    }<a name="line.279"></a>
<span class="sourceLineNo">280</span>  }<a name="line.280"></a>
<span class="sourceLineNo">281</span><a name="line.281"></a>
<span class="sourceLineNo">282</span>  /**<a name="line.282"></a>
<span class="sourceLineNo">283</span>   * Loads Finalizer directly using the current class loader. We won't be able to garbage collect<a name="line.283"></a>
<span class="sourceLineNo">284</span>   * this class loader, but at least the world doesn't end.<a name="line.284"></a>
<span class="sourceLineNo">285</span>   */<a name="line.285"></a>
<span class="sourceLineNo">286</span>  static class DirectLoader implements FinalizerLoader {<a name="line.286"></a>
<span class="sourceLineNo">287</span>    @Override<a name="line.287"></a>
<span class="sourceLineNo">288</span>    public Class&lt;?&gt; loadFinalizer() {<a name="line.288"></a>
<span class="sourceLineNo">289</span>      try {<a name="line.289"></a>
<span class="sourceLineNo">290</span>        return Class.forName(FINALIZER_CLASS_NAME);<a name="line.290"></a>
<span class="sourceLineNo">291</span>      } catch (ClassNotFoundException e) {<a name="line.291"></a>
<span class="sourceLineNo">292</span>        throw new AssertionError(e);<a name="line.292"></a>
<span class="sourceLineNo">293</span>      }<a name="line.293"></a>
<span class="sourceLineNo">294</span>    }<a name="line.294"></a>
<span class="sourceLineNo">295</span>  }<a name="line.295"></a>
<span class="sourceLineNo">296</span><a name="line.296"></a>
<span class="sourceLineNo">297</span>  /**<a name="line.297"></a>
<span class="sourceLineNo">298</span>   * Looks up Finalizer.startFinalizer().<a name="line.298"></a>
<span class="sourceLineNo">299</span>   */<a name="line.299"></a>
<span class="sourceLineNo">300</span>  static Method getStartFinalizer(Class&lt;?&gt; finalizer) {<a name="line.300"></a>
<span class="sourceLineNo">301</span>    try {<a name="line.301"></a>
<span class="sourceLineNo">302</span>      return finalizer.getMethod(<a name="line.302"></a>
<span class="sourceLineNo">303</span>          "startFinalizer",<a name="line.303"></a>
<span class="sourceLineNo">304</span>          Class.class,<a name="line.304"></a>
<span class="sourceLineNo">305</span>          ReferenceQueue.class,<a name="line.305"></a>
<span class="sourceLineNo">306</span>          PhantomReference.class);<a name="line.306"></a>
<span class="sourceLineNo">307</span>    } catch (NoSuchMethodException e) {<a name="line.307"></a>
<span class="sourceLineNo">308</span>      throw new AssertionError(e);<a name="line.308"></a>
<span class="sourceLineNo">309</span>    }<a name="line.309"></a>
<span class="sourceLineNo">310</span>  }<a name="line.310"></a>
<span class="sourceLineNo">311</span>}<a name="line.311"></a>




























































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